Browsing by Author "Roesner, Larry A., advisor"
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Item Open Access An evaluation of hydraulic retention time on BMP water quality performance(Colorado State University. Libraries, 2011) Messamer, Jason, author; Roesner, Larry A., advisor; Stednick, John D., committee member; Carlson, Kenneth H., committee memberUrban stormwater contains elevated concentrations of pollutants that are carried to receiving waters as runoff travels over roads, rooftops, and other hard surfaces. Structural best management practices (BMPs) are used to mitigate the negative impacts of urbanization by improving the water quality of stormwater runoff. Volume-based BMPs attenuate the peak flow of runoff and increase the hydraulic retention time (HRT) of runoff allowing pollutants to be removed through settling, adsorption, and other physiochemical processes. When BMPs provide longer HRTs for runoff events, the capacity for pollutant removal is increased because there is greater opportunity for pollutants to settle out of the water column and more time for plant and biological uptake. However, increasing the HRT that a BMP provides requires more storage volume, costs more to construct, and takes away land that could be developed for other uses. There is a tradeoff between the size of a BMP, the cost to build a BMP, and the capacity for pollutant removal. Two regional BMPs that serve the downtown area of Fort Collins, CO, were investigated in an effort to relate the HRT of a BMP to its water quality performance. The Udall Natural Area (Udall WP) is a wet extended detention basin that provided storm HRTs of over 80 hours. Contrastingly, the Howes St. BMP has an unregulated outlet and provided storm HRTs less than 20 hours. Stormwater quality data was collected from 2009-2011 at the inlet and outlet of each facility. The pollutant removal at each BMP was quantified for various runoff constituents including heavy metals, total suspended solids (TSS), bacteria, and nutrients. The Udall WP consistently had cleaner TSS effluent than the Howes St. BMP had and also removed significant amounts of heavy metals. The cleaner effluent at the Udall WP can be attributed to the longer HRT that the BMP provided. If the Howes St. BMP were modified to have a water quality outlet, it is believed that the BMP could enhance water quality more consistently and that it would actually be more cost-effective than the Udall WP. Furthermore, the degree of pollutant removal from the undersized and unregulated outlet at the Howes St. BMP was enough to warrant the suggestion that the Udall WP was constructed larger than necessary for significant pollutant removal. To further develop the relationship between HRT and water quality enhancement, additional stormwater studies for wet ponds and extended detention basins were investigated from the International BMP Database. A lognormal approximation was used to estimate the average HRT provided by a BMP based on the volume of runoff recorded at the BMP inlet during a storm event. The computed storm HRTs were matched with effluent water quality results for TSS, total recoverable zinc, total recoverable copper, and total phosphorous. Results were binned into HRT groups and a statistical analysis was conducted to determine whether longer HRTs enhanced the water quality at the BMP outlet. The analysis did not focus on water quality enhancement from inlet to outlet, but was aimed at determining whether additional treatment occurred from longer HRTs at the outlet. The results indicated that additional pollutant removal was not achieved in wet ponds when HRTs longer than 12 hours were provided. The only exception was total phosphorous, which was statistically lower in concentration when extremely long HRTs were provided. For dry extended detention basins, better pollutant removal was achieved when longer HRTs were provided, and longer HRTs (greater than 60 hours) may be required if total phosphorous or heavy metal reduction is desired. The findings could be used to refine BMP design criteria for the optimal HRT that will provide significant enhancements in water quality.Item Open Access Analysis and evaluation of stormwater quantity and quality performance for three permeable pavement systems in Fort Collins, Colorado(Colorado State University. Libraries, 2013) Gruber, Eli, author; Roesner, Larry A., advisor; Grigg, Neil S., committee member; Shuler, Scott, committee memberUrbanization and the subsequent increase of effective impervious area (EIA) result in an increase in storm runoff volumes, peak flow rates and pollutant concentrations. Stormwater management has recently shifted towards a focus on site level low impact development (LID) techniques that aim to reduce the total stormwater runoff volumes in addition to attenuating peak flows and removing pollutants at or near the source of runoff. Permeable pavement systems (PPS) are a subset of LID stormwater best management practices (BMPs) of particular interest in dense urban areas because they can be installed in parking areas and low traffic roadways where the availability of land space for more traditional BMPs is not available. However, few studies have documented the performance of PPS in terms of reducing runoff volume, peak flow and pollutant loads in semi-arid environments such as Colorado. Such information is necessary to improve the selection of BMP/LIDs for stormwater management. Three PPS in Fort Collins, Colorado were monitored between 2009 and 2011 to evaluate pollutant reduction, runoff volume reduction performance and surface infiltration rates. The Mountain and Walnut permeable inter-locking concrete paver (PICP) sites, referred to collectively as Mitchell Block, were each designed with differing "no-infiltration" sub-base designs to compare performance between a system with a sand filter layer (Walnut) and one with only gravel layers (Mountain). The third site, referred to as CTL, is a porous concrete (PC) parking lot that allows full infiltration, and was only monitored for water quality and surface infiltration rates. Mountain, Walnut and CTL all had lower effluent median event mean concentrations (EMCs) than those found at two Fort Collins stormwater outfalls for; total suspended solids (TSS), total recoverable zinc (TR Zn), total phosphorous (TP), total nitrogen (TN), total organic nitrogen (TON), total Kjeldahl nitrogen (TKN) and ammonia (NH3). EMCs for TR copper (Cu), nitrate (NO3) and total dissolved solids (TDS) at all three sites were elevated compared to the outfall sites. The TR Cu result EMCs at the three PPS were elevated compared to effluent PPS data from the International Stormwater BMP Database, which may indicate higher source concentrations in these study areas. CTL had elevated TR chromium (Cr) concentrations, which is likely a function of the portland cement in the PC itself, leaching Cr into the exfiltrate. Walnut had lower effluent median EMCs for 10 of the 13 water quality parameters analyzed, including significantly lower concentrations for TON, TKN and TR Cu. Recorded effluent volumes and estimated influent volumes to the PPS at the Mitchell Block sites were used to calculate runoff volume reduction on an event-based and long-term basis. Both sites provided runoff reduction for over 70% of the monitored events, with Mountain and Walnut reducing 45% and 35% of the total runoff volume monitored at each site, respectively. These results confirm that "no-infiltration" PPS designs are capable of reducing large volumes of storm runoff. Field capacity (water retention capacity) of the two sites was investigated with regard to runoff reduction. Runoff volume reduction at Mountain exceeded the field capacity for the two longest storms monitored. This suggests that runoff volume reduction potential can exceed field capacity given long intermittent rainfall events. An investigation of hydrologic storm parameters indicated a discernible trend between runoff volume reduction and antecedent dry time, showing increasing runoff volume reduction with increasing antecedent dry time. The runoff volume reduction performance at Mountain was greater than Walnut based on 23% greater median and average volume reduction per storm in addition to 25% greater total aggregate volume reduction for common monitored events at the two sites. This study did not investigate the design characteristics that allowed Mountain to provide greater runoff volume reduction. Surface infiltration rates at all three sites were estimated using a single infiltrometer field test. The results indicated that sections of all three sites are experiencing varying degrees of clogging. CTL had the highest degree of clogging, with two of the three tests indicating zero infiltration. Maintenance is recommended to reduce clogging for all three sites.Item Open Access Assessing the suitability for urban stream rehabilitation in Fort Collins based on watershed, hydrologic, and benthic macroinvertebrate indicators(Colorado State University. Libraries, 2010) Roznowski, Steven K., author; Roesner, Larry A., advisor; Kondratieff, B. C. (Boris C.), committee member; RamÃrez, Jorge A., committee memberDevelopment in urban areas generally increases the proportion of a watershed that is covered by impervious surfaces. This added impervious area causes both the quantity and peak rate of stormwater runoff to increase thereby altering the natural flow regime in receiving streams and causing changes in sediment transport. Such changes in hydrology and sediment load can adversely affect benthic macroinvertebrates residing in channel beds. This study assesses the degree to which watershed development has impacted urban streams in Fort Collins, Colorado and recommends areas for rehabilitation that are most likely to benefit from watershed or in-stream modification. Fort Collins has recently begun implementing best management practices (BMPs) to help control stormwater runoff from developed areas. Locations and coverage of BMPs along with other measures of urbanization are compared to available stream flow and shear stress data which are in-turn related to benthic macroinvertebrate indicators. By drawing comparisons between these parameters, the effectiveness of stormwater BMPs can be assessed. This allows for recommendations to be made which direct stream rehabilitation efforts in the City. The impacts of irrigation flows in the Fort Collins area were found to limit the effectiveness of BMPs. This irrigation influence made trends difficult to establish between benthic macroinvertebrate indicators and watershed characteristics. However, as evidenced by recent improvements in macroinvertebrate indicators at one location, the combination of BMPs and in-stream improvement can create habitat suitable for rich macroinvertebrate communities provided irrigation flows are controlled. Therefore, the locations with large portions of the watershed protected by water quality BMPs and relatively little irrigation impact are targeted as prime locations for in-stream rehabilitation. For areas with low levels of water quality control, it is suggested that water quality BMPs be added before in-stream rehabilitation is undertaken.Item Open Access Comparing multi-level and full spectrum detention design for urban stormwater detention facilities(Colorado State University. Libraries, 2010) Zhang, Xiaoju, author; Roesner, Larry A., advisor; Willson, Bryan D., advisor; Grigg, Neil S., committee member; Kampf, Stephanie, committee memberPeak flow attenuation and water quality control are widely used in urban stormwater systems. Standard practice typically involves peak shaving of post-development flows to pre-development peak flow levels to control flood flows and best management practices (BMPs) for removing pollutants from runoff. Usually both practices are integrated by using Multi-level Detention ponds. Recently, Wulliman and Urbonas (2005 and 2007) have proposed the so-called Full Spectrum Detention approach to design detention facilities able to control runoff events. This method is based on the concept of capturing the Excess Urban Runoff Volume (EURV) that results from urbanization and releasing it over a period of 72 hours. This method has been tested successfully for the Denver region and excellent matching of post-development peak flows to pre-development peak flows has been achieved. However, these results have been obtained using discrete design storms and the model has not been studied using a continuous simulation approach. Continuous simulations are useful because they provide information about the long-term performance through peak flow exceedance frequency and flow duration curves. Moreover, these results can be used to define the stream erosion potential, a metric that characterizes the geomorphic stability of urban streams. Continuous simulation has been successfully used to characterize the performance of Multi-level Detention method, which uses combined peak shaving and extended detention practices, and protocols to reduce urbanization impacts in different locations have been demonstrated with it. This study compares the effectiveness and differences of the Multi-level Detention design approach with that of the Full Spectrum Detention approach through the use of design storms and 60-year continuous precipitation records in a conceptual watershed for two different climate regions in the United States. The US EPA Stormwater Management Model (SWMM) is used to simulate the response of a conceptual watershed using both design approaches. Sensitivity analysis of the land-use properties is performed in order to validate the assumptions of the Full Spectrum Detention method by using both Colorado Unit Hydrograph Procedure (CUHP) and SWMM models. The performances of these two design approaches are tested initially by comparing the post-development peak flows for different design storms with the pre-development conditions. Additionally, 60 years of hourly rainfall records are used to run continuous simulations and compute peak flow frequency exceedance curves, flow duration curves, the hydrologic metrics T0.5, and average boundary shear stress curves, which are used to compute the stream erosion potential. The differences of both design methods are assessed by comparing the post-development results with those obtained for the pre-development conditions.Item Open Access Design and implementation of hydrologic unit watersheds for rainfall-runoff modeling in urban areas(Colorado State University. Libraries, 2009) Rivas Acosta, Iván, author; Roesner, Larry A., advisorThe calibration of complex hydrology and hydraulics of rainfall-runoff models represents one of the most challenging problems in water resources engineering. Unlike undeveloped watersheds, but specifically urban basins with surface drainage. From the available models, SWMM (Storm Water Management Model) was used as the modeling engine since it was developed for urban watersheds. Calibration procedure used a Multi-Criteria Decision Analysis (MCDA) approach that minimized the RMSE (Root Mean Square Error) between the flow duration curves of the modeled and the observed runoff. The flow duration curve was divided in High and Low Flows using the 1-Yr storm to split the curve, since there is a change in flow regime at this point. Pareto optimal front surfaces were obtained. Two case studies in North Carolina (Pigeon and SW Prong basins) were used to illustrate a proposed methodology for calibration. The methodology simplified the drainage network and irregular sub-catchments shapes were converted to regular shapes using a Kinematic Wave (KW) cascading plane approach. The KW cascading plane approach showed to be effective to convert irregular sub-basins shapes to rectangular features. A discretization analysis was performed where a set of hydrologic experiments using different levels of discretization were used and a threshold discretization value in urban hydrology was investigated. Needed GIS data was extracted through a toolbox. MCDA methodology and numerical simulations showed that Horton's decay coefficient (K, 1/h) and drying time (Tw, days) needed to have different values for the High and Low Flow portions of the flow duration curve to improve performance. Longer drying times were required to improve estimation of High Flows than Low Flows because the soils would take more time to recover their initial infiltration capacity. The Representative Element Area (REA) concept was explored in SWMM and it was found that sub-catchment sizes of 3% of the total basin size were appropriate. This magnitude represents the suggested level of discretization in urban watersheds since the improvement in performance became asymptotic either to 1.00 (Pearson's Moment Correlation Coefficient-PMCC, Nash-Sutcliff Coefficient-NSC and Index of Agreement-IOA) or to zero (RMSE) and therefore, it is not significant to improve the spatial resolution. Coarser resolution levels underestimated peak flow rates and total runoff volumes. Research results are summarized in a proposed protocol to discretisize urban watersheds.Item Open Access Development of a watershed modeling selection program and simple equations as an alternative to complex watershed modeling(Colorado State University. Libraries, 2013) Cho, Yongdeok, author; Roesner, Larry A., advisor; Grigg, Neil S., committee member; Arabi, Mazdak, committee member; Stednick, John, committee memberPopulation pressures, land-use conversion and its resulting pollution consequences appear to be the major diffuse pollution problems of today. Research also indicates that the increase in imperviousness of land due to urbanization increases the volume, rate of stormwater runoff causing increased channel erosion and flooding downstream, water quality contamination, aquatic biota, and drinking water supplies. In the past, negative impacts were never seriously considered as urbanization increased, but the attitude of citizens and governments are changing and people now want to retain, restore or rehabilitate existing waterways, and manage future urban and rural development in order to improve environmental conditions. Water quality management in the contributing watersheds is vital to the management of water quality in the main stem rivers. Hence, policy makers should decide which places should be considered for restoration projects based on priority analyses. To carry out these evaluations in Korea, mathematical models are needed to forecast the environmental results after applying watershed restoration measures. However, the scope of sophisticated watershed modeling is very complicated, expensive and time consuming, and not really required for planning level decision making. Therefore, simpler evaluation methods should be applied, that can adequately discern for planning purposes the changes in aquatic environmental quality that can be expected in different watersheds after adapting restoration or protective measures. Thus, this research proposed to create a simple equation specifically for watershed planning. To create such a simple equation, three main tasks were undertaken. The tasks are as follows: (1) the creation of a selection program for available watershed models, (2) establish simple equations to be used instead of watershed models, and (3) verify the simple equations by comparing them with a physically based model (HSPF). In regards to the first task mentioned above, this dissertation presents a review of thirty three watershed models available for watershed planning and shows that these watershed models can not easily be applied to large-scale planning projects that are being undertaken by South Korea like the Four River Restoration Project. One of the main reasons for their inapplicability is that they require vast amounts of data and significant application effort to be used in a prioritization project involving many watersheds (Roesner, personal commucation). In addition, it is vital to select an appropriate watershed model that are realistically models a watershed's conditions and more specifically, to match users' needs. However a selection program has not yet developed, as well. Therefore, eight factors were selected for task 1 to examine the specific characteristics of each of the 33 watershed models in great detail. Based on the results of the 8 factors proposed, the selection program was developed to screen which will be most useful to a project. Based on these literature reviews of the 33 available watershed models but unrealistically complex models, it was determined that a simpler model utilizing accessible base data, such as land use type, is needed to evaluate and prioritize watersheds in the feasibility stage of a spatially large projectstudies for national based projects (i.e. National level). A correlation study between land use types and water quality parameters has been published (Tu, 2011, Mehaffey et al., 2005, Schoonover et al., 2005, etc.), however, the research examined the correlation between land usage and water quality in great detail, but did not address any correlations to implement real-based watersheds. Therefore, Task 2 is the development of simple equstions, for this task, two important sub-tasks were undertaken 1) Hydrology (rainfall), geology (slope), and land usage data were analyzed to verify their relationships with the water quality (BOD, COD, T-N, T-P) in the watershed, and 2) Simple Equations were constructed based on Statistical Methods (Excel Solver, Statistical Analysis Systems) and Data Mining (Model Tree, Artificial Neural Network, and Radial Based Function) in order to prove their accuracy. Thus, if the equations are accurate, they can be used to prioritize basins within a watershed with respect to their impact on water quality in the mainstem river. For the final task, task 3, Simple Equations were verified by comparing them with a physically based model, HSPF, based upon the real-based watersheds which are located in South Korea in order to prove the Simple Equations are capable of being a reliable alternative to physically based models. These simple equations could be used to allow management to identify and prioritize restoration and rehabilitation areas in a watershed even though sufficient data had yet been collected to satisfy the requirements of a physically based model.Item Open Access Graywater research findings at the residential level(Colorado State University. Libraries, 2014) Marjoram, Christine, author; Roesner, Larry A., advisor; Sharvelle, Sybil, advisor; Klein, Donald, committee memberAs populations continue to grow and water supply sources become more stressed, innovative means for reducing our reliance on municipal water are becoming more prevalent. Graywater reuse is one water conservation practice which has the potential of reducing household water demands by 30% indoors and outdoors, depending upon irrigation demands. In areas where water scarcity is an ongoing challenge, implementation of graywater reuse practices is becoming more widely accepted. However, constituents commonly found in graywater may pose a threat to the environment or human health. The objective of this thesis is to present graywater research findings from 2003 to the present which have occurred as part of a graywater research program at Colorado State University. The research findings address issues and concerns raised regarding graywater and present the case for graywater reuse being a viable safe, simple and economical technology. In order for graywater reuse applications to continue to expand, the concerns regarding public health risks raised by regulating agencies and public health officials need to be fully addressed. Early research on a residential pilot graywater system for outdoor irrigation formed the foundation for more recent research targeting effects on soil quality (chemistry and microbiology), plant health, groundwater contamination, graywater quality and potential human health risks (Sharvelle, 2009, Shogbon, 2010, Neghaban-Azar, 2012). An optimal residential graywater system prototype for drip irrigation has been developed (Alkhatib, 2008) which includes two tanks, one for collection, coarse filtration and settling and the other for usable storage. The WERF study (Sharvelle et al., 2012) showed no need for disinfection of graywater being used for irrigation. The presence and levels of pathogens on field sites whether being irrigated with either municipal water or graywater were the same. The WERF research (Sharvelle et al., 2012) coupled with the prototype configuration supports no need for inclusion of disinfection as part of the treatment train when graywater is being applied for irrigation. The most recent research is a multi-residential graywater reuse demonstration project for toilet flushing completed on Colorado State University campus, Aspen Hall (Hodgson, 2012). Graywater used for toilet flushing will require a higher level of treatment due to the increased potential for exposure. Hodgson studied and selected Chlorine as the disinfectant for the residence hall. The resulting water quality with storage, filtration and disinfection determined by Hodgson achieves similar results as found in the 2003 residential pilot graywater system research which used UV rather than chlorine. The difficulty of navigating the varying graywater regulations between states drove Glenn's research (2012) into the graywater requirements for each state and who developed a tool for use by regulators to homeowners for finding an appropriate graywater technology to meet their local requirements. Also, a need was identified for providing a comprehensive guidance manual for separating graywater from blackwater for graywater reuse (Bergdolt, 2011). The manual provides design guidance and maintenance best management practices to ensure safe and appropriate graywater installation and operation.Item Open Access Graywater reuse guidance and demonstration using a constructed wetland treatment system(Colorado State University. Libraries, 2011) Bergdolt, Jesse Hawk, author; Sharvelle, Sybil E., advisor; Roesner, Larry A., advisor; Glick, Scott, committee memberCommunities throughout the United States and abroad are developing interest in innovative approaches to sustaining their freshwater resources. One method, graywater reuse for non-potable demands, is gaining popularity because it allows the reuse of minimally contaminated wash water generated at the home/office for non-potable demands, which then reduces the demand for treated water and preserves source waters. Graywater is defined as any wastewater generated at the home or office excluding water from the toilets, kitchen sinks, and dishwasher, but includes wastewater from the laundry, shower, and bathroom sinks. When compared to other wastewater generated in the home graywater is minimally contaminated with lower concentrations of organics, solids, nutrients, and pathogens, thereby rendering the water suitable for reuse with minimal treatment when compared to other domestic wastewater sources. Despite widespread interest in this innovative approach information on the separation and design of residential and/or commercial scale graywater systems have been limited. The objective of this study was 1) to provide a graywater reuse manual for home or business owners interested in separating sources of graywater from blackwater for graywater reuse and 2) to determine the first order removal rates (k) of graywater constituents using both a free water surface (FWS) and subsurface flow (SF) constructed wetlands, in order to provide design guidance for future constructed wetlands that will be used to treat graywater. Information regarding the separation and reuse of graywater is important to the success of graywater reuse systems. This thesis provides information to business and home owners about the separation of graywater from blackwater for graywater reuse. Part one of this thesis outlines the methods and equipment needed to install a dual plumbing system for the purpose of graywater reuse. Part one also describes how to design an individual graywater reuse system specific to the needs of the home or business owners, the technologies and equipment necessary for graywater reuse systems, known maintenance requirements for graywater systems, and best management practices to ensure safe reuse of graywater. Individual graywater reuse systems for the home or office are too small to treat large amounts of graywater produced by residential neighborhoods or communities. Consideration should be given to treatment options that can handle and treat a large amount of graywater. Constructed wetlands can offer a scalable, economically sound, low tech and easily maintained method of treating graywater for large scale irrigation reuse. While constructed wetlands are an appropriate technology for graywater treatment there is little research providing the removal rates for the design of constructed wetlands for graywater reuse. Determining removal rates is important for creating wetland design standards for graywater treatment and reuse. Part two of this thesis provides the experimental results for determining the seasonal flow adjusted removal rates (k) of graywater constituents using a free water surface (FWS) constructed wetland and a subsurface flow (SF) constructed wetland. Removal rates were evaluated over a two year period (2008-2010) for a FWS wetland and evaluated over the summer/fall of 2010 for a SF wetland. The results for the FWS included the biochemical oxygen demand (BOD5) removal rates of 15.9 (m yr-1) for summer removal, 15.2(m yr-1) for fall removal, and 5.6 (m yr-1) for winter/spring removal. The total nitrogen (TN) removal rates were 16.4 (m yr-1) for summer removal, 8.5 (m yr-1) for fall removal, and 5.5 (m yr-1) for winter removal. The total organic carbon (TOC) removal rates were 10.4 (m yr-1) for summer removal and inconclusive for the TOC removal in the fall and winter seasons. The results for the SF during the summer included a BOD5 removal rate of 19.1 (m yr-1), a TOC removal of 22.8 (m yr-1), a TN removal rate of 21.3 (m yr-1), and an ammonia removal rate of 32.6 (m yr-1). The results were inconclusive for the fall season due to a limited amount of data. When compared to other literature k values for sizing wetland for agricultural and municipal wastewater, results from this study had lower k values for BOD, which resulted in a larger required surface area (SA) for wetland design. The TN and ammonia k values were comparable to other literature design values.Item Open Access Investigating the efficacy of graywater use at the household level(Colorado State University. Libraries, 2008) Alkhatib, Ramadan Y., author; Roesner, Larry A., advisorThe use of graywater at the household level is gaining increasing popularity in both the United States and elsewhere. The treatment methods in the market are either too simple or too complicated for a household resident to use. Also, the effects of using graywater in landscape irrigation and the fate of chemicals in graywater are still unclear. The socio-economic aspects of graywater are variable from one place to another and need to be investigated in order to predict whether graywater use will be accepted or not by the people.Item Open Access Low impact development modeling to manage urban storm water runoff and restore predevelopment site hydrology(Colorado State University. Libraries, 2010) Simpson, Matthew G., author; Roesner, Larry A., advisor; Grigg, Neil S., committee member; Glick, Scott, committee memberThe hydrologic effects of urban development have been documented for some time. Urban streams experience dramatic changes to their natural flow regime, which is mostly due to the increased rate and volume of runoff. Conventional stormwater management focuses on peak rate control through the use of detention and retention basins while paying little attention to the increased volume of urban runoff. Low Impact Development (LID) is a land planning and stormwater management approach that seeks to control runoff as close as possible to its source. LID practices take advantage of natural processes, such as infiltration, to reduce the rate and volume of runoff while improving water quality at the same time. It is hypothesized that LID can be used to restore the predevelopment hydrology to a site. This thesis investigates if LID can be used exclusively to meet stormwater requirements and secondly whether LID can maintain the predevelopment site hydrology. In order to examine if LID can restore predevelopment site hydrology, an EPA SWMM model was created based upon a proposed development in Fort Collins, CO. Several different scenarios were evaluated including: rainfall from Fort Collins, CO and Atlanta, GA; a high and a low infiltration soil; and BMPs with partial infiltration (with underdrain) and with full infiltration (without underdrain). The amount of LID in each model was increased until predevelopment peak flow rates and water balance were met; this was accomplished using design storm simulations. Each model was then analyzed with a continuous simulation using historic rainfall data from both locations. The LID BMPs that were modeled include grassed swales, rain gardens, infiltration trenches, and permeable pavement. Finally, a cost review of the LID designs was performed to explore the financial practicality of LID. The results show that LID can restore predevelopment site hydrology, but the amount of LID required is substantial. However, the cost review shows that the extra LID expense could be recovered in certain locations through development of the detention pond land which is no longer needed.Item Open Access Morphologic characterization of urban watersheds and its use in quantifying hydrologic response(Colorado State University. Libraries, 2009) Gironás, Jorge, author; Roesner, Larry A., advisor; Niemann, Jeffrey D., advisor; RamÃrez, Jorge A., committee member; Stednick, John D., committee memberCurrent methods for hydrologic characterization of urban watersheds and analysis of the impacts of urbanization are primarily based on the description of imperviousness and how changes in this characteristic affect storage, infiltration, and runoff generation. The morphology of urban watersheds and the effects of urbanization on the structure of the drainage system have been much less studied. The overarching objectives of this study are to develop methodologies to characterize the morphology of urban drainage systems including the hillslopes, streets, pipes, and channels and to use this characterization to model the hydrologic response of the watershed. These objectives are accomplished through: (a) an exploration of potential applications of morphologic theories in the characterization of urban watersheds and the impacts of urbanization; (b) the development and testing of a methodology to generate urban terrains (i.e. a raster representation of the topography) in which the effects of conduits typically observed in urban areas are represented; and (c) the development and testing of a new rainfall-runoff model called the U-McIUH (Urban Morpho-climatic Instantaneous Unit Hydrograph). The model is based on the morpho-climatic instantaneous unit hydrograph theory, in which the hydrologic response is identified from the spatial structure of the watershed and the properties of the storm event. The morphologic approach adopted reveals significant impacts of urbanization on the internal structure of natural watersheds at a wide range of scales. This finding is relevant when building stormwater models intended to simulate and compare the pre- and post-development catchment response. The morphologic impacts should be incorporated into stormwater models through the redefinition of model parameters that characterize both the channelized and unchannelized portions of the catchment when the urbanized scenario is simulated. This research also shows the importance of incorporating artificial conduits into urban terrain for hydrologic modeling. A new method to incorporate the artificial conduits into the DEM based on the real elevation of these conduits proved to be superior to other previously available methods because it better represents the flow directions and flow paths. Finally, the new rainfall-runoff model developed in this study fills an existing gap in the field of distributed stormwater modeling. It provides a more thorough treatment of the flows in minor conduits and unchannelized portions of the watershed, which enhances the simulations of runoff accumulation that are traditionally used in conceptual models. The model is parsimonious and uses a simplification of kinematic wave routing that considers the dependence of the unit hydrograph on rainfall intensity and the effect of upstream contribution on the travel times without explicitly solving the flow equation at each cell for each time step. This simplification reduces the complexity of the model computations while still producing reasonable model performance.Item Open Access Performance modeling of stormwater best management practices with uncertainty analysis(Colorado State University. Libraries, 2009) Park, Daeryong, author; Roesner, Larry A., advisor; Loftis, Jim C., advisorBest management practices (BMPs) contain many uncertainties that make it difficult to determine their performance with a model. Moreover, predicting BMP performance with existing methods is not easy. The major research objective of this dissertation is to incorporate uncertainty analysis in a BMP performance model to better represent its treatment performance. The k-C* model is used in this study to simulate BMP performance, and the study assumes that the influent event mean concentration (Cin) and aerial removal constant (k) include uncertainty. Both Cin and k represent data and model uncertainty. To evaluate the model, three different uncertainty cases, uncertainty in Cin, k, and both Cin and k, are applied to the total suspended solid (TSS) data of detention basins and retention ponds. To evaluate uncertainty values, three different uncertainty analysis methods, the derived distribution method (DDM), the first-order second-moment method (FOSM), and the latin hypercube sampling (LHS), are applied to each case. TSS, as a representative pollutant, and detention basins and retention ponds, as representative BMPs, are utilized in this study. The observed datasets are selected from the International Stormwater BMP database. By incorporating uncertainty analysis into the k-C* model, the effect of BMP surface area and inflow on the effluent event mean concentration (Cout) of TSS can be quantified for detention basins and retention ponds. These effects are not large in detention basins but are noticeable in retention ponds. In addition, the k-C* model with uncertainty analysis is applied to a hypothetical watershed to show how uncertainty might be used improve the probability of compliance with TMDLs.Item Open Access Retrofitting a water quality control structure to maximize pollutant removal efficiency for an existing wetland(Colorado State University. Libraries, 2014) Trifone, Laurie, author; Roesner, Larry A., advisor; Sharvelle, Sybil, advisor; Laituri, Melinda, committee memberAn existing seven acre wetland captures stormwater runoff from a 505 acre watershed located in Fort Collins, CO. The wetland has shown measurable pollutant removal with its current outlet design, but the pollutant removal efficiency could be increased through the installation of a water quality control structure (WQCS). The wetland is bounded by an adjacent park, stream, bike path, and building limiting water quality improvement options. Thus, the wetland dimensions cannot be altered. The objective of this project is to design a water quality control structure that would maximize pollutant removal efficiency and the mass of total suspended solids (TSS) removed in the wetland without causing additional flooding at the site and adversely affecting the adjacent properties. An additional objective of this project was to develop a method to calculate the hydraulic retention time (HRT) for a stormwater wetland. EPA's Stormwater Management Model Version 5 was used to model the existing conditions and various proposed WQCS drawdown times. The modeled drawdown times ranged from 2 hours to 72 hours. Continuous simulation modeling was used because the wetland volume could not be adjusted to contain the water quality capture volume. It was assumed that all stormwater runoff entering the wetland was captured and treated. Using the model generated volume, depth, and flow data, the non-steady state hydraulic retention times and hydraulic loading rates (HLR) were calculated for each drawdown time analyzed. The k-C* method developed by Kadlec and Knight (1996) and measured data from the wetland were used to calculate the pollutant removal efficiency and the total annual TSS removed. The results indicate that a drawdown time of 30 hours will provide the best removal efficiency while considering the site constraints. The installation of the WQCS will have an HRT of approximately 14 hrs and increase the removal efficiency by 14.2% and the total annual TSS removed by 31,100 lbs from existing conditions. Furthermore, the addition of the WCQS will only increase the maximum flooding depth and duration at the overflow locations by a maximum of 0.02 ft and 0.2 hrs, respectively, for the 100yr storm event. For the 2yr storm event, the addition of the WCQS will only increase the maximum flooding depth and duration at the overflow locations by a maximum of 0.01 ft and 0.1 hrs, respectively. The depth of water in the wetland, for both storm events analyzed, will not exceed the wetlands embankment at any location besides the overflow locations. At brimful conditions, the detained runoff water remains in the main channel and permanent pool areas of the wetland. The methods developed in this project can be used to retrofit an existing wetland with a WQCS that would maximize removal efficiency while considering site constraints.